Just in time for that vote, a respected Mexican think tank found that legalizing pot in those states would cut Mexican drug lords' profits by as much as 30 percent.

That's a huge blow considering that cartels makes nearly $6 billion a year from drug trafficking, according to the RAND Corporation, the Associated Press reports.

But opponents to legalizing pot say that drug cartels could just set up business fronts in the U.S. states that have legalized marijuana and make up for their lost profits that way — this time, legally.